Looks like they rolled all their savings in to traditional IRAs and then converted them in to Roth IRAs. This procedure, known as a 'Backdoor Roth' conversion, effectively allows unlimited Roth IRA contributions beyond the income limits. If you are scratching your head and asking, why this is legal - so are many other people, but it appears to be accepted as within regulation by tax experts.
As for whether it ought to be legal, my view is that multiplication (of which both income taxation and compound investing returns are forms) is commutative and taxing an amount now (the conversion) and then having it grow for 20 years is no different than having it grow for 20 years and taxing it then (traditional IRA), assuming growth and tax rates remain the same.
A Roth conversion is in essence a bet on your marginal tax rate at withdrawal being higher than your marginal tax rate today.
So the 'backdoor' Roth contribution allows such people to invest post-tax dollars w/ Roth benefits when the IRS income limits seemingly make it clear that they shouldn't be able to contribute in this fashion. Why does the IRS have income limits on Roth IRA contributions but then allow them to be so easily bypassed in this manner?
> assuming growth and tax rates remain the same.
Big assumption.
I think TFA answers this. The limits were put in originally, and then as part of Bush-era tax cuts, as a way to raise current revenue, the conversion was allowed knowing that billions in taxes would be paid today in order to convert. They predicted $9 billion and got something like $30 billion instead.
Taxing the money now, when a large part of it could be passed via inheritance tax free later, is not necessarily bad policy.
I like cash over magical promises that can wiped away with the stroke of a pen.